The present invention relates to hand tools. In particular, the invention relates to a tool for installing and removing machine assembly devices known as retainer rings or snap rings.
Retainer rings are C-shaped springs, usually of a high carbon steel, for example, having a relatively thin cross-sectional thickness. In the thickness dimension, the ring is substantially constant. In the frontal plan, the C-shape is modified first, by the presence of small, tool pin apertures through lobes that terminate the horn ends of the C. Frequently, the web of the C-shape is wider through the bight of the C-shape. A wide bight thickness enhances the C-shape capacity to oppose forces on the C-shape having the effect of opening or closing the ring by spreading the C-shape horns.
Retainer rings are internal and external gender specific as to relative geometry. An external ring is positioned around the outer perimeter of an element having circular section such as a rod or shaft. The exact axial position for the ring is determined by a relatively shallow slot or groove that is cut, turned or otherwise formed around the shaft perimeter at the required position along the shaft axis. The slot width is only slightly greater than the ring width. The diameter of the shaft slot is therefor less at the bottom of the slot than the outside surface diameter of the shaft.
An external retainer ring is constructed with a partial circle internal perimeter having an inside diameter greater than the diameter of the shaft slot bottom but less than the outside diameter of the shaft. Consequently, the retainer ring horns must be spread to open the ring internal perimeter sufficiently to allow the ring to be passed axially over the shaft end, along the shaft length and into transverse planar alignment with the retainer slot. So aligned, the horn spreading stress is removed thereby permitting the retainer ring horns to return to their unstressed form within the retainer slot. The internal perimeter of the C-shape is below the shaft external surface whereas the external perimeter of the C-shape is above the shaft external surface. Consequently, the radial, fin-like projection of the retainer ring from the shaft surface presents a structural abutment to the relative axial displacement of bore elements around the shaft in at least one axial direction.
An internal retainer ring has a complimentary construction for positionment around the internal perimeter of a circular bore. A narrow shallow retainer slot is formed into the bore wall at the desired axial location. The partial circle of the retainer ring has a circular outer perimeter with a diameter slightly less than the internal diameter of the slot bottom but greater than the internal diameter of the bore wall. Consequently, the retainer ring horns are stressed inwardly to close the ring opening and reduce the ring outer perimeter for the purpose to inserting the ring axially along the bore to transverse planar alignment with the retainer slot. Here, the stress is released and the retainer ring is allowed to spring open into the retainer slot. However, the ring internal perimeter elements project radially from the retainer slot into the bore as abutments to prevent axial displacement of such machine elements as bearing races and shaft seals.
Both external and internal retainer rings are gripped for horn displacement by tool nibs that are inserted into a small circular aperture in each of a lobe element that is integrally formed at the end of each ring horn. Depending on whether the retainer ring is of the internal or external gender, the lobe area is turned inwardly or outwardly and does not invade the slot penetrating circle of the ring. Accordingly, the lobes are turned inside of the outside diameter of an internal retainer ring whereas the lobes of an external retainer ring are turned outside of the inside diameter of an external retainer ring. This geometry facilitates placement of the tool nib apertures at an accessible location relative to the respective shaft or bore surface elements.
The traditional retainer ring tool is a plier type implement having a pin projecting from each nib. This type of tool is suitable for manipulating small, easily accessible retainer rings. However, corrosion, physical damage and complex assembly challenges the utility of such tools. Since the gripping contact between the tool and the ring is only the engagement area between the tool nibs and the apertures in the ring lobes, there is little tolerance or accommodation for twisting and other assembly manipulations, usually employed under difficult circumstances. Moreover, large retainer rings require some sort of mechanical advantage for installation and removal.
As a further note on the prior art, plier type tools, with or without mechanical advantage, displace the retainer ring lobes along a chord line of the retainer slot having little radial component. If the slot is corroded, contaminated with fine grit or physically damaged as by peening along the retainer slot, a chord line displacement of the ring lobes is longer and more difficult than a radial displacement.
It is therefore, an object of the present invention to provide an improved retainer ring tool having positive pin movement for controlled ring location and placement.
Another object of the present invention is an improved retainer ring tool having utility in limited access areas.
A further object of the invention is an improved retainer ring tool that is designed for extended reach utility.
Also an object of the present invention is an improved retainer ring tool with replaceable ring lobe engagement nibs and replaceable arms for mounting the nibs.
Yet another object of the invention is an improved retainer ring tool designed to provide a more radial nib movement into and from a retainer slot for improved ring manipulation control.
Another object of the invention is a retainer ring tool having a right angle nib mounting arm designed for extended reach visibility.
Another object of the invention is an improved, ergonomically designed holding handle for a retainer ring tool.
Finally, an object of the invention is an ergonomically designed nib adjusting wheel for positive control of large, heavy duty retainer rings.